Patent GB-1062140-A (GB)
Title: Improvements in or relating to grinding fixtures
IPC: B24B41/06
Filed: 1965-11-23
Abstract: 1,062,140. Grinding; drills. DE VLIEG MACHINE CO. Nov. 23, 1965 [Dec. 30, 1964], No. 49778/65. Headings B3C and B3D. A grinding fixture 26 for grinding the working surfaces of a spade drill on a table type surface grinder comprises a tumble block having a front surface 30 provided with means 48 extending perpendicularly thereto for orienting the spade drill at predetermined angles relative to the surfaces of the tumble block, a first one 42 of the surfaces being formed at a predetermined angle relative to the plane of the front surface for orienting a first one of the working surfaces of the drill parallel to the table 12 of the surface grinder, a second one 44 of the surfaces being formed at another predetermined angle relative to the plane of the front surface for orienting a second one of the working surfaces of the drill parallel to the surface of the table, and means 56 fastenable to the front surface for securing the drill on the front surface orienting means and against the front surface. The surfaces 42, 44 are trapezoidal in shape, Fig. 7 (not shown), and extend between side surfaces 34, 36 which are at right angles to a back surface 32 and the front surface 30 and a top surface 38 is also at right angles to the side surfaces 34, 36. The front surface 30 is inclined to the back surface 32, Fig. 6 (not shown), and the orienting means consists of a ramp 28 having a surface 48 extending perpendicularly to the front surface. Any one of a number of differently-sized locating bars 52 according to the size of the drill to be ground can be secured to the front face and locates the drill by engaging a recess 55 in the base thereof, the drill being fastened to the surface by a clamping bar 56. The drill has a centre point 76, Figs. 2 and 3 (not shown) and leading edges 88, 90 adjacent primary relief surfaces 78, 80 which intersect secondary relief surfaces 82, 84. Chip-breaking grooves 96, 97 extend across the secondary relief surfaces at constant depth and are of varying depth across the primary relief surfaces. The drill also has a pair of wedge surfaces 104, 106 adjacent the point, outer guiding surfaces 110, 112 and diameter relief surfaces 114, 116. The drill is sharpened by being secured by the bar 56 to the front face 30 of the tumble block with the recess 55 engaged by one of the locating bars 52 and the block is placed with the first surface 42 on the table 12 which is in the form of a magnetic chuck and is energized to hold the block thereto with one of the primary relief surfaces parallel to the table surface. The table is then reciprocated to carry the drill past a vertically adjustable grinding wheel 16. Thereafter, the block is rocked so that the second surface 44 engages the table to permit the secondary relief surface associated with the previously ground primary relief surface to be parallel to the surface of the table 12 and be ground by the grinding wheel. The drill is then removed from the block and turned through 180 degrees for the grinding of the other primary and secondary relief surfaces. The chip-breaking grooves are ground by a profiled grinding wheel with the block mounted with its second surface 44 engaging the table, the block being turned through 90 degrees from the position shown in Fig. 1. As illustrated in Fig. 8 (not shown), each of the locating bars may have two pairs of locating surfaces and serve for locating one or other of a pair of differently sized drills.